Highly cost-effective analytical device for performing immunoassays with ultra high sensitivity

Abstract

A simple easy to manufacture analytical device capable of performing membrane based immunoassays on batch of samples within 3 to 10 minutes wherein the method permits focused application of samples, costly labeled immunoassay and signal amplification reagents, said device includes an antibody-immobilized micro porous membrane, breadth corner layer of which is directly attached to a semi-rigid liquid-impervious body with water insoluble adhesive; absorbent body is provided separately and is not attached to analytical device during manufacture, absorbent body is wetted and is placed proximal to the lower surface of the membrane thereby forming networks of capillary channels with the absorbent body; flow of samples or reagents is always kept downwards and focused without application of any force to the absorbent body and the use of disposable adsorbent body permits stepwise addition of signal amplification reagents for ultra sensitive detection of diagnostically important molecules by visual examination of the membrane surface.

1. A method for assembling an absorbent body of an analytical device comprising:
 a liquid-permeable porous reaction membrane having an upper and a lower surface, 
 an exposed area of the upper surface having immobilized thereupon an antibody or antigen capable of binding to the target analyte, wherein said immobilized antibody or antigen being concentrated in multiple spotted regions of the said upper surface, and a portion of the lower surface of the reaction membrane in breadth corner has no immobilized antigen or antibody; 
 a semi-rigid liquid impervious bottom support layer attached to the lower surface of the reaction membrane at the breadth corner by water insoluble adhesive or tape having glue on both sides; and 
 a body of absorbent material having an upper surface and a lower surface, capable of absorbing liquid, wherein the body of absorbent material is provided separately from the analytical device and in use, the absorbent material is pre-wetted with a liquid and is placed between and in contact with the reaction membrane, which is above the body of the absorbent material and the bottom support layer, which is below the body of the absorbent material, and the body of absorbent material is capable of absorbing liquid and is larger in size than the reaction membrane, 
 (a) soaking the absorbent body with liquid and assembled in such a way that the upper surface of the absorbent body is in intimate contact with the lower surface of the reaction membrane and the upper surface of the bottom support layer, 
 (b) removing the entrapped air in between the lower and the upper surface of the absorbent body by pressing the upper surface of the reaction membrane, 
 (c) the void volume of the reaction membrane is saturated and the distance separating the reactive membrane and the absorbent body is such that a network of capillary channels is formed when the two members are in contact, 
 (d) the flow of applied sample or reagent is always downwards and focused without application of any force to the absorbent body, and 
 (e) the void volume of the wetted absorbent body is sufficient to substantially absorbs a predetermine volume of fluid sample. 
 
     
     
       2. The method as claimed in  claim 1  wherein, the absorbent body is soaked in deionized distilled water or buffer. 
     
     
       3. The method as claimed in  claim 1  wherein, the upper surface of the reaction membrane is pressed with small roller or rimless small test tube. 
     
     
       4. The method as claimed in  claim 1  wherein, pre-wetted absorbent body saturates the void volume of reaction membrane.